1. Field of the Invention
The subject invention relates to a stent and graft assembly for treating vascular anomalies, such as aneurysms.
2. Description of the Related Art
Vascular anomalies are considered to include blood vessels that are damaged, weakened or otherwise impaired. The anomaly may include a local change in the cross-sectional dimensions of the blood vessel. For example, aneurysms include a local area where a blood vessel expands to a larger cross-sectional area due to disease, weakening or other damage.
The aorta extends from the heart and through the abdomen. The abdominal aorta then feeds abdominal organs and the right and left iliac arteries that bring blood to the right and left legs respectively. The aorta is prone to aneurysms. Aortic aneurysms that are not treated in a timely manner can lead to rupture, occlusion, infection or the production of emboli which can flow downstream and occlude a smaller blood vessel. A ruptured aortic aneurysm typically is fatal due to a loss of the large volume of blood that flows through the abdominal aorta.
Aneurysms can be corrected by grafts. The typical graft is implanted surgically by accessing the site of the aneurysm, cutting open the aneurysm and then surgically forming an appropriate fabric into a tubular shape that spans the aneurysm. Thus, upstream and downstream ends of the prior art graft are sutured to healthier regions of the blood vessel.
The prior art also includes endovascular grafts. An endovascular graft comprises a flexible tubular member formed from a synthetic fabric. The graft is selected to have an outside cross-sectional dimension that approximates the inside cross-sectional dimensions of the blood vessel on either side of the aneurysm. The graft also is selected to have a length that exceeds the length of the damaged area of the blood vessel.
An unsupported flexible tubular graft has a tendency to collapse in the presence of the flowing blood and could be transported downstream by the blood flow. As a result, endovascular grafts are used in combination with a stent. Stents take many forms, including balloon expandable stents and self-expanding stents, but typically are resilient cylindrical members that are inserted axially through the tubular graft prior to insertion into the blood vessel. The stent and the graft are sutured together prior to deployment so that the opposed ends of the stent align with the opposed ends of the graft. The endovascular graft assembly then is inserted through a healthy region of the blood vessel and is advanced through the circulatory system to the aneurysm or other damaged region of the blood vessel. More particularly, the endovascular graft assembly is advanced to a position where the endovascular graft assembly bridges the aneurysm or other damaged portion of the blood vessel. However, the opposed axial ends of the endovascular graft assembly extend beyond the aneurysm. The stent then is expanded to hold the graft in an expanded tubular condition with at least the opposed axial end regions of the graft being urged tightly against the interior of healthy regions of the blood vessel. The stent and the graft of the prior art endovascular graft assembly are coaxial, and longitudinally coextensive.
Prior art assemblies of stents and grafts typically perform well. However, the coaxially and longitudinally coextensive arrangement of the stent and graft has resulted in a cross-sectionally large assembly. A cross-sectionally large graft and stent assembly can be difficult to insert and deliver intravascularly to the damaged section of the blood vessel and may require surgery.
The inventor herein has developed low-profile stent/graft structures, as shown for example in U.S. Pat. No. 6,015,422, U.S. Pat. No. 6,102,918 and U.S. Pat. No. 6,168,620.
In view of the above, it is an object of the subject invention to provide improvements in vascular stent and graft assemblies that provide a small cross-section and low profile.
It is also an object of the invention to provide an endovascular stent and graft assembly that can be introduced easily into and through the damaged or diseased section of a blood vessel.
A further object of the subject invention is to provide a system of endovascular stents and grafts that can be assembled intravascularly through damaged regions of a blood vessel.